Rail clamp for traveling bridges



Jan. 15, 1935. B, H. KERSTING RAIL CLAMP FOR TRAVELING BRIDGES Filed March 22. 1933 4 Sheets-Sheet l EL!!! E INVENTOR Jan. 15, 1935. B, H. KERSTING RAIL CLAMP FOR TRAVELING BRIDGES 4 Sheets-Sheet 2 INVENTOR flwmfl. A6112: 6&4176/ "Jww? Filed March 22, 1933 Jan. 15, 1935. a H. KERSTING RAIL CLAMP FOR TRAVELING BRIDGES 1935 Shee'ts-Sheet 3 Filed March 22 Jan. 15, 1935. B H E N 1,988,173

RAIL CLAMP FOR TRAVELING BRIDGES Filed March 22, 1933 4 Sheets-Sheet 4 INVENTOR Kim/1f I Patented Jan. 15, 1935 UNITED STATES PATENT OFFICE Bernard H. Kersting, Ben Avon, .PaL, assign! to The Dravo Contracting Company, a corporation of Pennsylvania Application March 22, 1933, Serial NoLGBZJM .8 Claims.

bridge to which the invention is applied; Figs. 11

and III are sections .on the planes indicated by the lines II-1I and III-'III, respectively, Fig. I; Fig. IV is a fragmentary view in side elevation, and to larger scale, showing the rail-clamp mechanism which is associated with each leg of the bridge; V is a view in planiromabove of the structure of Fig. IV; Fig. VI is a view in vertical and transverse sections of the structure shown I in Fig. .IV, the plane of section being indicated at VI.VI, Fig. IV; Fig. VII is .a view in section, taken .on the plane VIIr-W'JI, showing to larger scale the lower portion of a leg of the bridge; Fig. VIII is afragmentary view, showing to larger scale a portion of the assembly as seen in Fig. IV; and Fig. IX is a wiring diagram.

Referring to F gs. I, II, and III, the numeral 2 designates a carriage in the form of a traveling bridge having legs 3 and 4, through which the bridge rests on trucks 5, and the trucks v5 move on rails 6 on the two sides of (for example) an ore pile P. This bridge is shown to be provided with a clamshell bucket 7, and with the usual operators cab 8. Associated with each truck is a rail-clamping mechanism, in which mechanism the invention is embodied.

The clamping mechanism of each truck (cf. Figs. IV, V, and VI) includes two parts or elements, 10 and 11, each of which includes a pair of railwengaging clamps. The two elements 10 and 11 of each truck are operated by a motor 12 borne by the truck, and the motors 12 of opposite trucks are energized from a common supply line (cf. Fig. IX). A drum 19, whose shaft 18 is borne in suitable bearing in the truck 5, is arranged with its axis of rotation transverse to the direction of bridge travel, and direct driving connection is provided between the motor 12 and the drum 19, through which, in response to motor rotation, the drum may be rotated in clockwise direction (Fig. IV) at a speed suitably related to the speed of the motor.

The two clamping elements 10 and 11 borne by each truck are essentially alike, and it will suffice to describe the element 11 in detail.

A pair of equal, symmetrically formed clamping layers 28 and 29 are pivoted .unon bins 32 in a pair of links 31, that together constitute a. fulcrum block. .The linksex'tend horizontally, and the levers swing in vertical plane, perpendicular to the line of extent of a rail 6. The levers are symmetrically arranged with respect to the'vertical mid-plane of the rail 6; thelrlong power arms extend upwardly, their s'hortwork arms downwardly, and the work arms terminate in jaws 30 disposed on opposite sides of rail 6. The llnksill are supported in the structure in such mannerthat, l0 whileheld against downward displacement, they float horizontally, in the direction of their length-4n a direction, that'is to say, p rp ndicular to the extent of rail 6. By the swinging of the levers the jaws alternately close with clamp ing effect upon the rail and recede from such 'engagement; and by the floating movement of the links 31 small irregularities in relative positions of parts find compensation, and the clamping action is always efiective, with equal and opposite thrusts upon opposite sides otthe rail.

Forthe support of the links 31, a plate 37 depends from the frame 01' the truck in the vertical mid-plane of the rail. This plate is recessed in its lower portion, asindicated at 11, and on-opposl'te sides of the recess the plate carries transversely and vertically extending plates 35. Against their opposing faces the two plates 35 early 36, and the horizontally extending upper edges of strips 36 aflord bearing surfaces upon which the links ,31, by virtue ofv their laterally directed flanges 33, may rest and move.

The range of floating movement of links 31 (sufficient for practical purposes) is limited, and the integrity of the assemblyis assured, by Iorming in plates 35 and strips 36 elongate openings 34, through which the prolonged pivot-pins 32 extend.

Formed in the truck 5 is. a guideway that extends vertically above the rail, and in this guide- 40 way a power block 80 is mounted to move vertically. This power block 80 is connected by equal and symmetrically extending links 81 to the power arms of the levers 28 and 29. The block 80 carries wheels 800. which co-operate with vertical guides 80b, to insure free vertical movement .of the block during the operation ofthe clamping mechanism. It will be perceived that, as block 80 is shifted vertically up and down, the rail clamp swings in opposite opening and closing directions. The block 80 is backed by springs 52, which tend always to expand and to close the clamp and to hold the jaws 30 in engagement uponthe rail 6. The opening of the jaws against thetension of spring 52 is eifected by the motor 12. It will further be remarked that the force exerted by the springs 52 tends always to maintain the links 31 centered in the vertical line of power block movement: any shifting of these links transversely upon their ledges is met by an excess of spring tension exerted in opposite direction.

Upoiithepowrfarms of th'el levers28 and 2's sheaves 22 and 21 are rotatablym'ounted. Aline 2O anchored at one end to a trunnion of one of the sheaves is reeved around the sheaves, as shown in Fig. VI, and extends thence by way of suitable guide sheaves to the drum 19, upon which it is wrapped and to which 'atzits end it is secured. As the drum 19' is by *the'motor1'2 driven in clockwise direction (Fig. IV) the line 20 is wrapped upon drum 19,;thepower: arms of the levers 28 and 29 are drawn together, the block 80 rises (the compression of springs 52 being in-'- creased), and the jawsSO open.

1" Whenthe jawsare thus opened, a magnetically set brake76, (,effectivejupon the shaft'of motor 12+ cf;FigsQIvgV, andIX) closes,'tolock the motor and drurn'jagainst rotation and to hold "theclamp in its position of release. At the same time a'jswitch 73 swings, deenergizing the motor. When. any of the several conditions, presently to ,be'd'escribed, prevails, to effect release of the brake, thespring's 52 become effective, to shift the block ,80 downward, to spread the power- ,arrns oi the leversZBand 29, andto cause the jaws 30 to close with clamping effect upon the .track' 6. 'During'lsuch downward movementof thejblock the'rope 20 is drawn away from the dru'mQcausing the drum and motor to turn in a counterclockwise direction (Fig. IV), against the resistance, however, of. a dynamic brake, to be falluded to again below. 7, M Associated with each of the two clamping mechanisms of. each truck is' a limit switch 61 (cf. Fig.1IX) Each limit switch is located in a from the normal closed positionjindi'cated in-Fig.

IX to the'alternateopen position. Inthe closed position of the clamp, the finger b'orneby the block 80 is free of contact with the limit switch; the switch memberel then stands in closed position. .When underthedriving power of motor 12 theshe'aves 21and 22 have been drawn together and'the b1ock,8 has been forced upward against spring tension, and the clamp opened,

contactflof the movable finger 82 (borne by block 80) with the limit switch will have effected ,the

opening of switch member 61.

"f v.Fig'. IX-is a wiring diagram of the twomotors 12 which are mountedone on each of the trucks at the opposite ends of the bridge. Referring to this wiring diagram, the motor 12 of the clamping mechanisms 10 and 11 for the leg 3 of the bridge is adapted to'be connected by means of an interlocking magnetic switch '73 with the positive ;and negative feed linesa and b. A foot switch ,,67,locate'd in the operatoris cab, is adapted to e1ose thecoil of a magnetic switch 70 in circuit withthe power supply lines (P. S.) for the bridge,

"and the consequent energizing "and closing of the switch 70 effects the connection of the feed lines 1a,]? withthe power supplying liness P. S The ,inotore12 of the clamping mechanisms for the flegf eoi, the bridge is (by meansof a duplicate "set of switches 73, 67) at the will of the operator adapted to be connected in circuit with the feed lines 0, b. It will, therefore, be understood that the motors 12 and the clamping mechanisms at each end of the bridge are subject to either joint or several operations.

When the operator desires to move the bridge along therails 6, he closes the two foot-switches 67'. @This completes circuits 'throu'gh' magnet coils 68 and causes the switches '70, "normally held open, to close. The closing of the switches 70 completes a circuit through the magnet coils 72 of the'interlocking switches in the two motor circuits, causing the arms 73a of switches 73 to shift to the upperf of their alternate positions, whereby the circuits from the feed lines (a b c) are closed through the motors. Electric current is then effective to energize the motors and to turn the drums 19 (in clockwise direction, as seen in Fig. IV), thus drawing the sheaves 21 and 22 of each clamp together, raising theblocks 80, compressing the spring 52, and opening the clamps, When the clamps have been moved to fUHYr-ODED. position, the engagement of the movable fingers 82 on the blocks so with their associate limit switches 61' will efiect the swinging of the switch elements to open position, whereby the circuit to the magnet coil 72 is broken and the arms 73a of the interlocking switches drop to 1pletesthe energizing circuits for the magnetic brakes 76, while the simultaneous energizing of coils 86 actuates the circuit closers 87 and brings the usual controls (not shown) for the bridgemoving motors into communication with the feed lines a 1). Thus, it will be perceived that when,

due to the action of the motor 12, the blocks 80 reach the top of their vertical travel, and eifect the opening of the limit switches 61, the brake 76 is energized and locks the clamping mechaing circuits for the motors are interrupted, due to the falling of switch arms 73a to their lower positions, and the controls for the bridge-moving motors are brought into circuit with the feed lines. Manifestly, so long as either clamp of truck 5 is closed upon the railsan'd, indeed, until both clamps of the truckare fully opened and the brake 76 appliedthe bridge-moving motor cannot be energized. This feature is of notable value in practice."

When the operator removes his foot from either switch 67, the switch opens, thereby breaking either the circuit ab or the circuit bc. Consequently, the magnetic brake 76 is deenergized and released, and the springs 52 immediately become effective to shift the blocks80 downward in their ways andto close the clamps upon the rails.

At the same time the cables 20 and 56 are out furtherprovision suihcient to obviate the ob-- jectionable violence. In solving the problem, a particularly effective use is made of motor 12. The motor 12 is so wired that when its shaft turns backwardunderthe pull of cables 20, 56 it becomes an electric generator and great torque is required nism in release. At the same time the energiz- 1:6 turn its" retor. This torque produces a drag that"v automatically increases as rotor speed increases. hi'i'othervaluable feature of delayin the closihgpi" the" clamps is that time is allowed for the bridgeto drift to a stop. Accordingly, a-graduated braking eflect is produced upon the clamps as they advance to closed position. When the clamps reach hill rail-clamping position, the motor 12 comes to rest and the braking drag created byfit when' in motion becomes nil. I

" To the end that the generator braking may be efl'eeted wlthoutinjury to the motor, a: resistance R'iil ig"; IX) is includedin the motor circuit. The resistances, indeechis in effect two resistances 1'1 and r2; resistance 11 is connected in series with the motor supply line and is effective while the motor operates for the purpose primarily inte'ndedz' the opening of the rail-clamps. The resistance T2 is arranged in shunt across the motor terminals, andwhen' the rotor is turned backward uhder the pull of the cables 20, 56, the circuit through the resistance 1'2 constitutes the motor a generator; The resistance 12 then affords an electric load and'afiords insurance that amperage of damaging magnitude shall not flow through armature or field coils oi. the motor.

' .Still'cdns'ide ring Fig. IX of the drawings, it will be observed that a magnetic switch '18 is interposed in circuit between feed lines (a b c) and the magnet coils of switches 73a, '75, 87. The

switch 781s nem to closed position by the energizin'g" of its coil '79 and this is effected so long as a switch 89 continues in its normally closed positioh. The operation of the bridge then is effected in-Ithe manner already described. When, however, the coil '79 of switch 78 is de-energized and the switch is shifted to open position, the circuits to coils 72, 77, and as may not be completed and the corresponding switches 73a, '75, and 87' may not be'closed. Thus, when the switch '78 is open, the bridge-moving motors may not be energized, none of the clamp-opening motors 12 may be energized, and neither of the magnetic brakes '76 may be operated. In a word, regardless of the use to which the bridge may at a particular moment be applied, when the switch '78 opens, the bridge-moving motors and the clamp-releasing parts'become incapable of operation. The clamps .thcn engage the rails and continue to engage the rails until the switch '78 again is closed.

The invention includes means responsive to high wind for opening the switch '78, and thus safeguarding the bridge against injury. Advantageously, an anemometer W isperched upon the superstructure of thebridge (Fig. I). The wind wheel w (Fig. IX) of the anemometer is secured to or geared to the shaft of a small dynamo d,

and the poles of the dynamo are connected in circuit with the operating coil of switch 89; the

switch 89 controls the circuit for energizing the coil '19 of switch '78. The switch 89 is normally closed, but is so designed electrically that, when the wind wheel turns at or above a predetermined speed, the switch 89 opens. In consequence, the switch '78 opens, operation of the bridge ceases, and the clamps close upon the rails, or, if the clamps are at the time closed, the motors 12 may not be operated to open them, until the wind has "subsided. Thus, it will be seen that the bridge may not be operated when the velocity of wind exceeds a predetermined value. The same conditions hold true when the supply voltage fails in ranged oneach truck 5, so that the'l'egs 3 and 4 of the bridge may be shifted independently'along the tracks 6. I

The amount of this shifting (skewing) of the bridge islimited by means ofa skew limit switch, which; has the function of disconnecting the. current from the motor at the end? of the bridge in motion, or in case where both ends'are in motionone end moving faster than the otherthe advancing end ofthe bridge will be'flrst slowed down and then brought to rest, until the other end has advanced within the allowable skew limit. The skew limit switches are not shown inthe drawings, this skewing feature of construction being well known in the art. However, it isto accommodate skewing that the clamping mechanisms 10, 11 are independently operable at each end of the bridge, there being a separate switch 6'7 in the cab for each set of clamping mechanisms. If both ends of the bridge are to be moved simultaneously, the operator simply depresses both switches 6'7.

In bridges of long span it is impracticable with interdependent clamps at the opposite ends of the bridge to maintain the bridge true upon its tracks; accordingly, skewing is by the independence of the clamps recognized, and its effect corrected. Skewing also is advantageous when the bucket is to collect material from a wider area and, carrying it longitudinally of the bridge, deposit it again to a hopper or other receptacle. bridge can remain stationary at one end, spotted over a hopper, and the other end may range over a stock pile.

By the present invention I have provided an extremely eflicient rail-clamp mechanism which,

due to the simplicity of its construction and light weight and to the absence of clamp weights, is

relatively inexpensive to manufacture and to inthem. By reason of the lazy-tongs arrangement,

through-which the tension of the spring is made effective, the spring exerts a powerful closing force upon the clamp levers. Furthermore, by providing apair of springs 52 for each pair of clamp jaws, exerting their tension in unison upon the clamp levers, tending to spread the power arms of the clamp levers, the individual springs need not be made so heavy as a single spring would necessarily be in order to perform the same work- It will be remarked of the springs 52 that they are assembled between the block 80 and a backing-plate 54 by means of keeper bolts 51. In the erection the springs are assembled with the block 80, the backing-plate 54, and the bolts 51, and these elements are introduced as an assembled unit. The bolts afiordmeans for rehaving the tension of the springs when repair is to be made. It will be noted that the lazytongs arrangement is such that the. power is transmitted with increasing effect; as the jaws move toward the rail. Thisis highly desirable,

because the spring-means employed for closing the jaws inherently exerts a decreasing force as the spring expands. By combining the spring, which is a source of power of decreasing value, with lazy tongs, which, as they swing, are increasingly responsive to the power, the proper clamping action is assured. The arrangement of lazy tongs and spring, so that the mechanical advantage of the lazy tongs varies inversely with the power of the spring, is important also in the jaw-opening operation. Once the opening jaws are clear of the rail, it will be desirable that as little work as possible .be done in maintaining the jaws in open position. Considering the lazy tongs from this point of view, it will be apparent that a decreasing force is required to open the jaws, and that a relatively small forcewill be eifectivei in maintaining the, jaws in open position. Thus it appears that the lazy tongs, combined with the spring in the manner described, is of importance and value both in the closing and in the opening of the jaws.

I claim as my invention: v v I v 1. In rail-clamping mechanism thecombination, with a movable carriage and a rail extending adjacent the carriage and in the direction of carriage movement, of a clamping device including a pair of clamping levers fulcrumed in said carriage and adapted in the assembly to swing between rail-clamping and rail-releasing positions, means tending to hold the clamping device in rail-clamping position, means for shifting the said clamping device to rail-releasing position, such means including an electric circuit, and an electric motor and a magnetic brake arranged in parallel in said circuit, a switch adapted to be engaged and swung by said rail-clamping device and adapted in its: swing to break the circuit through the motor and to make the circuit through the brake, and means for breaking the circuit simultaneously through both motor and brake.

2. A rail-clamping device for a traveling bridge includingin combination with a bridge traveling upon two spaced-apart legs, of two rails extending in the direction of crane travel, one adjacent each of the said legs, a pair of clamping levers fulcrumed pair by'pair in the two legs and adapted in the assembly to swing in planes transverse to the direction ofbridge travel and to engage the rails, pair by pair, simultaneously upon opposite sides, means tending to hold the levers to rail-engagement, and severally operable means for rendering each of the last-named means inefiective and for swinging the levers of one pair to rail-releasing positions.

3. -In a traveling bridge standing upon and movable upon a pair of spaced-apart legs, two rails extending in the direction of bridge movement and arranged, one adjacent each of the said legs, two pairs of clamping levers mounted, one pair in each of the said legs and adapted to swing between rail-clamping and rail-releasing positions, .two electrically controlled means one such means associated with each pair of levers for swinging "said levers from rail-clamping to rail-releasing positions, and two switches standing sition by the muscular effort of an attendant, the two said electrically controlled means associated with the two pairs 'of levers, otherwise inefiective, being rendered severally effective on the closure severally of the two said switches,

4. A rail clamp for traveling carriages including, in combinaiton with'a rail and a carriage movable thereon, of a bearing member with uph line of extent of the said rail, adapted to j'sw'ing in such plane and by simultaneous and opposite.

swinging, by their downward-extending work arms alternately to engage and to release said rail, a guideway in said carriage extending vertically above said rail, a power block movable in said guideway, a pair of equal links pivoted symmetrically to said power block and one to each of the clamping levers in the power arms thereof, yielding means engaging said block and tending always to shift said block downward in its guideway and tending always to maintain the said fulcrum block centered in its range of movement in the vertical line of power-block movement, and means for exerting upon the upwardly extending power arms of said clamping levers simultaneous opposite and equal clamp-opening stresses.

5. In rail-clamping mechanism the combination, with a movable carriage and a rail extending adjacent to the carriage and in the direction of carriage movement, of rail-clamping means, means tending to hold the rail-clamping means in rail-clamping position, a clamp-releasing electric motor, an electrically operated brake for said motor, means driven by said motor for swinging said rail-clamping means to release position, a source of electric energy, wiring, and a switch, the parts being so arranged that, an electric cir cuit being established from the source of energy through said wiring and through said motor, the clamp-releasing means in their movement to clamp-releasing position engage and I shift the switch, whereby the motor is deenergized and the brake is through said wiring brought into circuit with the source of electric energy.

6. In rail-clamping mechanism the combination, with a movable carriage and a rail extending adjacent to the carriage and in the direction of carriage movement, of rail-clamping means, means tending to hold the rail-clamping means in rail-clamping position, a' clamp-releasing electric motor, an electrically operated brake for said motor, means driven by said motor for swinging said rail-clamping means to release position, a carriage-moving electric motor, a source of electric energy, wiring, and a switch, the parts being so arranged that; an electric circuit being established from the source of energy through said wiring and through the clamp-releasing motor, the clamp-releasing means in their movement to clamp-releasing position engage and shift the switch, whereby the clamp-releasing motor is deenergized, the brake is energized and applied, and the carriage-moving motor is brought into circuit energy.

7. In rail-clamping mechanism the combination, with a movable carriage and arail extendwith the sourceof electric ing adjacent to the carriage andin the direction of carriage movement, 01' rail-clamping means, means tending to hold the rail-clamping means in rail-clamping position, an electric motor, a normally open and magnetically applied brake for the rotor of the said motor, and means arranged between the rotor of the motor and the rail-clamping means whereby forward turning of the rotor effects opening swing of the rail-clamping means and closing swing of the rail-clamping means effects backward turning of the rotor and a magnetic retardation upon the closing of the clamping means, a source of electric energy, wiring, and a switch, the parts being so arranged that, an electric circuit being established from said source of energy through said wiring and through said motor, the consequent opening swing of the rail-clamping means throws the switch, whereby the motor is deenergized and the brake is through said wiring brought into circuit with the source of electric energy, together with a second switch arranged in said wiring and within the circuit last defined, whereby, the parts being in the positions last defined, the brake will on the swinging of the switch be deenergized and rendered ineffective and the means tending to hold the rail-clamping means in rail-clamping position will then, subject to the electric drag of the rotor, effect the closing of the rail-clamping means.

8. In rail-clamping mechanism the combination, with a movable carriage and a rail extending adjacent to the carriage and in the direction of carriage movement, of rail-clamping means, means tending to hold the rail-clamping means in rail-clamping position, an electric motor, a normally open and magnetically applied brake for the rotor of the said motor, and means arranged between the rotor of the motor and the rail-clamping means whereby forward turning of the rotor efiects opening swing of the railclamping means and closing swing of the railclamping means eiiects backward turning of the rotor and a magnetic retardation upon the closing of the clamping means, a source of electric energy, wiring, and a switch, the parts being so arranged that, an electric circuit being established from said source of energy through said wiring and through said motor, the consequent opening swing of the rail-clamping means throws the switch, whereby the motor is deenergized and the brake is through said wiring brought into circuit with the source of electric energy, together with a second normally open and magnetically closed switch arranged in said wiring and within the circuit last defined, whereby, the parts being in the positions last defined, on failure of power the said second switch will open, the aforesaid brake will be deenergized and the rail-clamping means under magnetic retardation will close.

BERNARD H. KERSTING. 

